1. Field of the Invention
The present invention pertains to methods and means for automatically assembling and nailing together wood frame components, and more particularly, it pertains to methods and means for assembling and nailing together the component parts of conventional wooden pallets which are comprised of a plurality of parallel spaced stringers interconnected by one or more sets of parallel spaced deck boards.
2. Description of the Prior Art
Wooden pallets, which are used to support stacked loads of goods, have become increasingly important to many phases of industry due to a general trend toward automated material handling systems to reduce the time consuming costly manual labor involved in hand stacking and transporting operations. Although pallets may come in a variety of specific designs, the most commonly used type basically comprises a series of spaced wooden stringers which are secured together in parallel relationship by a plurality of aligned deck boards running crosswise to both their top and bottom side edges. Due to the heavy demand for such structures, pallet manufacturers have long been seeking methods and means to efficiently increase their production rates without the addition of offsetting increased labor costs. These heavy labor costs are primarily due to the time and the number of men needed in the assembly of and the nailing together of the various component parts of the pallets.
Various automated pallet assembling systems have been proposed in the past, one such system being shown in U.S. Pat. No. 3,557,439 to Dykeman, which issued on Jan. 26, 1971. The pallet assembling system disclosed in that patent generally comprises a continuous flow system wherein two automatic nailing machines are utilized for separately nailing the deck boards on each side of the stringers. A turnover device is arranged between the nailing machines to automatically flip the half-finished pallet over so that the second set of deck boards can be readily placed atop the unnailed faces of the stringers. The assembling system as disclosed in aforementioned Dykeman patent, however, does not include means for automatically assembling the stringers and the deck boards. Since these component parts of the pallet have to be placed by hand into an assembly jig before the jig can be moved to the nailing machine, the time required for the pallet making operation is not as fast as it might otherwise be with a fully automatic operation.
In recent years, other complete pallet nailing systems have been provided which utilize two nailing machines and wherein the deck boards and the stringers are separately fed into the nailing machines and automatically assembled therein prior to nailing. In one such system, the two nailing machines are aligned in a straight line path and are each provided with special deck board feeders which operate to automatically slide an entire set of deck boards over to the nailing anvils of the nailing machines in position to be nailed to the underlying stringers. The stringers are separately and individually located in pockets on a stringer conveyor which carries them beneath the aligned deck boards and, through appropriate control means, stops in the proper positions for nailing. Such pallet nailing system has not achieved wide popularity in the pallet making industry, however, since at least five men are required to load the deck boards and stringers for an efficient operation. Also, operational problems of various types have been encountered with such system.